UN projections estimate that the world's population, at 5.5 billion in 1993, will reach 11 billion by 2050 although the figure could be anywhere from 5 billion to 20 billion.
Different parts of the world differ widely in their fertility rates.
In 1993 sub-Saharan Africa had a fertility rate of more than 6, India 4, China 2.4, U.K. 1.8, West Germany 1.4, and Italy/Spain 1.2.
As a general rule highly developed industrialized countries have lower birth rates and underdeveloped rural countries have higher birth rates although governmental and cultural influences play a role.
Strong governmental programs providing sex education and promoting contraception and equality for women in a Moslem country, Tunisia, brought the birth rate down from 45 per 1,000 to 24.4 per 1,000 between 1963 and 1994.
In Moslem and Roman Catholic countries religious authorities may be in conflict with governmental attempts to control population growth, but sex education and contraception programs have been effective in Iran (average growth rate 1988-3.9%, 1994-1.8%) and Brazil (fertility rate 1970-5.8%, 1975- 4.3%, 1984-3.6%).
Immigration is a factor in reducing population of underdeveloped countries and increasing population in developed countries that offer economic opportunity.
Scotland, for example, reversed a long-standing yearly decline in population in 1991 with an influx of immigrants.
Birth control in the west and Japan is creating aging societies and shortage of younger laborers while developing nations produce more people than they can accommodate, thus fueling immigration.
